Temperature characteristics of magnetoelectric interaction in langatate-ferromagnet composite resonators

Magnetoelectric interaction in a layered langatate-hysteretic ferromagnet structure is observed with no bias magnetic field applied. The temperature characteristics of interaction are determined mainly by the properties of the ferromagnetic layer. Raising the temperature weakens the coupling between layers and lowers the efficiency of interaction.     

Whispering gallery modes in nonideal disk resonators

We consider the problem of the whispering gallery mode in resonators having the shape of a circular segment close to a disk or a half-disk. The calculations are performed using perturbation theory methods.     

Magnetoelastic mechanism of magnetoelectric interaction

The magnetoelastic mechanism of the magnetoelectric interaction characterized by the energy ?_mu is analyzed theoretically. This interaction is described in terms of the expansion of the magnetic energy ?_m in powers of components of the vectors u _j (displacements of crystal lattice sites from equilibrium positions) rather than the vectors ?_u, which determine the magnetostriction component ?_ms of the magnetoelastic energy. One more difference between the energies ?_mu and ?_ms lies in the fact that the magnetoelectric energy ?_mu corresponds to the interaction of magnetic excitations with optical phonons, whereas the magnetostriction energy ?_ms corresponds to the interaction of magnetic excitations only with acoustic phonons. It is established that the magnetoelectric interaction is affected by the electroactive optical phonons (interacting with the electric field), which, as a rule, make a small contribution to the total number of optical branches of the phonon spectrum. The magnetoelectric energy ?_mu is described within the approach in which all nonelectroactive branches of optical phonons are automatically excluded from consideration. This approach is based on the concept of the electric sublattice formed by all chemically identical ions with equal valences. Analysis is performed using the Fe₂TeO₆ compound as an example.     

Nonlinear magnetoelectric effect in composite multiferroics

The theoretical and experimental studies of the nonlinear magnetoelectric effect in composite multiferroics in the low-frequency spectral region and in the electromechanical resonance region have been performed. It has been shown that such structures demonstrate a nonlinear magnetoelectric effect, which is quadratic in ac magnetic field strength at weak magnetic fields. In the region of the electromechanical resonance, the resonance excitation of an electric field occurs by means of ac magnetic field at a frequency lower than the resonance frequency by a factor of two. In the low-frequency spectral region, there is a difference of amplitude values of two neighboring voltage maxima due to the superposition of signals from the linear and nonlinear effects, and the difference is proportional to the dc magnetic field strength in weak fields. The results of the experimental study of the two-layer permendur-lead zirconate titanate structure are presented.     

Surface-roughness-induced contradirectional coupling in ring and disk resonators

Reflections that are due to random surface roughness in periodic structures such as dielectric rings and disks inherently phase match forward- and backward-propagating modes. Small reflections are thus considerably enhanced and may impair the performance of traveling-wave resonators. In addition, such contradirectional coupling leads to a splitting of the resonant peak. These effects are studied analytically.     

Effect of an electric field on the characteristics of magnetoelectric interaction in a ferromagnet-ferroelectric composite structure

The characteristics of the magnetoelectric interaction in a planar nickel-lead-zirconate-titanate structure have been studied in a dc electric field applied to the ferroelectric layer. A hysteretic field dependence of the efficiency and frequency of the resonant magnetoelectric interaction has been revealed, and the vanishing of the interaction efficiency in the range of polarization switching fields due to changes in the permittivity, the piezoelectric modulus, and the dielectric loss of the ferroelectric has been observed. It has been shown that the electric field leads to a significant change in the rigidity of the ferroelectric layer.     

Nonlinear magnetoelectric interactions in composite multiferroic structures

A theory of magnetoelectric interactions in ferromagnetic-ferroelectric composite structures is presented. Resonant frequency doubling and magnetic field mixing effects in the planar structure of a lead zirconate-titanate amorphous ferromagnetic film are investigated experimentally.     

Nonlinear magnetoelectric response of a bulk magnetostrictive-piezoelectric composite

Magnetoelectric effect in a bulk composite of nickel ferrite and lead zirconate titanate has been investigated by applying an ac magnetic field with no bias field. The measurements were carried out in the low-frequency region for harmonic magnetic field modulation with amplitude up to 3 kOe. The electric field induced by out-of-plane magnetic field exceeds that induced by in-plane magnetic field by approximately 4 times. Nonlinearity of ferrite magnetostriction of the sample results in a doubling in the frequency and a strong distortion of the ME signals. The magnetically induced voltage can be found by integrating the ordinary ME voltage coefficient over magnetic field.     

Parametric interaction and magnetodielectric resonators

Moscow State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 3, pp. 292–300, March, 1991.     

Low-frequency magnetoelectric effect in a Galfenol-PZT planar composite structure

The forward and inverse magnetoelectric (ME) effects are experimentally studied in a two-layer planar structure containing mechanically coupled Galfenol and PZT plates. The process of production of polycrystalline Galfenol plates and their magnetic and magnetostriction characteristics are described. For the forward ME conversion, the dependences of the amplitude of the voltage generated by the structure on the magnitude and orientation of a dc magnetic field and the frequency and amplitude of a modulating magnetic field are measured. For the inverse ME conversion, the dependences of the amplitude of the change in the magnetic induction of the structure on the dc magnetic field and the frequency of an ac electric field applied to the structure are measured. The efficiencies of the forward and inverse ME conversion are estimated for the case of low-frequency field modulation and under conditions of the resonance excitation of bending and longitudinal mechanical vibrations in the structure.     

Improvement of fabrication and characterization methods for micromechanical disk resonators

In this paper we present a novel method to fabricate reliable micro-electro-mechanical system(MEMS) disk resonators with high yield and good performance.The key breakthrough in the fabrication process is a novel approach to effectively restraining electro-chemical corrosion of polycrystalline silicon(polysilicon) electrically coupled with noble metals of MEMS devices by hydrofluoric acid(HF)-based solutions.In addition,a measurement architecture based on a differential readout topology is demonstrated.The differential circuit proposed here can effectively suppress noise and feed-through current by common-mode rejection of the differential amplifier.This differential amplifier circuit configuration is also used to build up a notch filter.The preliminary result about the temperature dependence of the resonance frequency is discussed,and the device failure is analysed.     

Frequency response of magnetoelectric effect in piezoelectric-magnetostrictive disk-ring composite structures

A theoretical model is presented for frequency dependence of magnetoelectric (ME) effect in piezoelectric-magnetostrictive disk-ring composite structures. Expressions for ME voltage coefficients in piezoelectric-magnetostrictive (PE-MS) disk-ring and MS-PE disk-ring are obtained by solving elastodynamic equations. The calculated resonance frequency and frequency dependence of ME voltage coefficients are in good agreement with the experimental results. This model indicates better mechanical coupling in disk-ring structure than that in traditional layered structure, and this may be responsible for the enhancing ME effect. The analysis suggests the disk-ring composites structures are promising for magnetoelectric applications.     

层状磁电复合材料谐振频率下的巨磁电容效应

对三明治复合结构Tb_xDy_1-xFe_2-y/Pb(Zr, Ti)O₃/Tb_xDy_1-xFe_2-y的电容与频率及磁场的函数关系进行了实验和理论研究. 实验发现,该复合材料样品的电容随频率的增加而出现多个谐振峰,并且其谐振点随磁场的增加而发生频移. 在谐振点附近,观察到样品的阻抗随磁场的增加由容抗性转变为感抗性,从而同时观察到巨大的正磁电容效应和负磁电容效应. 由复合材料的弹性力学本构方程出发,对该类样品的电容随频率及磁场的变化进行了理论模拟. 结果显示,模拟曲线与实验结果符合得很好. 理论表明该磁致伸缩/压电复合材料的磁电容效应源于磁场诱变的铁磁相柔顺系数. 关键词： 层状复合材料 界面弹性耦合 磁电容效应     

Observation of second-order hyper-Raman generation in LiNbO3 whispering-gallery mode disk resonators

In this Letter we report experimental demonstration of nonlinear frequency conversion at several optical frequencies in a whispering-gallery mode resonator (WGMR). Because of the enhancement of nonlinear interactions inside a WGMR, interaction of a 1064 nm pump field with a LiNbO(3) disk produced a weak but measurable non-phase-matched 532 nm second-harmonic field at room temperature (>100 °C below the phase-matching temperature) for pump powers of a few tens of milliwatts. For higher pump powers, we observed the generation of four additional fields at 545, 559, 573, and 587 nm. The relative spectral shift between two consecutive fields corresponds to a 455 cm(-1) vibrational mode in LiNbO(3) crystal. Our preliminary analysis indicates that these fields are the result of a multiphonon hyper-Raman scattering in which two photons of the pump field are converted into one photon of a higher-frequency field and one or several optical phonons.     

Terfenol-D/PZT磁电复合材料的磁电相位移动研究

采用粘合法制备了叠层结构的块体Terfenol-D/PZT磁电复合材料,测量了不同频率下的磁电回线,采用新的极坐标下的方式做图.从极坐标下的磁电回线中可以看出,随直流磁场的变化,非谐振频率下的磁电相位发生了轻微移动,移动幅度随频率的增加而增加;而在谐振频率下,伴随着巨磁电效应,磁电相位发生了显著移动,移动幅度达到了近90°.与粉末Terfenol-D/环氧树脂/PZT磁电复合材料对比之后表明,非谐振频率下块体Terfenol-D/PZT的磁电相位移动主要由涡流引起;而谐振频率下大幅度相位移动则主要来源于Terfenol-D的磁致弹性变化.     

Extended verification of scaling behavior in split-ring resonators

We present an expanded LC-model for nanoscale split-ring resonators (SRR), including the influence of dielectric host materials. The LC-model is experimentally verified by changing the geometry of the SRR unit cell as well as by optofluidic tuning, where the SRR samples are covered with index oil. The extended model can be used as a general guideline for metal SRR structures with arbitrary dielectric host materials.     

Dynamics of domain walls in weak ferromagnets with quadratic magnetoelectric interaction

The dynamics of domain walls of the ab type in weak ferromagnets with a quadratic magnetoelectric interaction has been studied in ac magnetic and electric fields. The specific features of the vibrational and drift motions of the domain walls as functions of parameters of the external fields and characteristics of the material have been discussed. The possibility of drift occuring the domain walls in a purely electric field has been predicted.     

Surface dynamics of a nongyrotropic multiferroic with quadratic magnetoelectric interaction

The effect of quadratic magnetoelectric interaction on the conditions of propagation and localization of one-partial polariton and elastic surface waves has been studied by the example of a bounded centrosymmetric easy-axis ferroelectric antiferromagnet.     

Wave interaction in acoustic resonators with and without hysteresis

Nonlinear interaction of counterpropagating waves in solids is considered by using a general approach taking into account only the cumulative (resonant) nonlinear perturbations giving a nonzero contribution over the period and, consecutively, potentially able to significantly modify the linear solution. Different stress-strain relations are addressed, including those with hysteresis which serve as basic models for the recent acoustic experiments with rock and metals. An important case of the interaction of counterpropagating waves with close amplitudes in a high-Q resonator (bar) with hysteresis is specially addressed and compared with the case of a ring resonator.